Introduction

FTOOLS is a collection of utility programs used to create, examine, or
modify the contents of FITS data files. There are also user
friendly GUI tools which allow interactive browsing of FITS files
and provide a more intuitive interface for running the FTOOLS.
The FTOOLS package forms the core of the
HEASARC
software system for reducing and analyzing data in the FITS format.

Each FTOOLS task is a separate program that performs a single simple
operation. The FTOOLS are primarily a Unix based package, although a Windows
version was created for version 4.2 (a 5.0 version is in the works). Most
of the powerful GUI interfaces run only on Unix, although the core
GUI tool, fv, is available for Unix, Windows, and MacOS.
Further discussion of supported platforms is available in the
FTOOLS FAQ. Scripts are available for
combining several FTOOLS to perform complex tasks.
All of the core FTOOLS programs share several common design features:

All are written in ANSI Fortran or C;

All use a simple standardized subroutine interface for getting the
value of program parameters
(e.g., the name of the input FITS file), and;

All scripts are written in
Perl5 (although many will work in Perl4). Note: The
official Perl5.001 release doesn't work with all
ftools scripts (due to a bug in the Perl code). To run ftools
perl scripts, you will need "unofficial patchlevel" 5.001m or
higher.

The GUI tools are written in Tcl/Tk: Currently there are
fv (an interactive FITS file browser/editor)
and xdf
(the XTE Data Finder). The FTOOLS distribution contains the
source for the Tcl/Tk interpreters that these tools need to run and
will build them for you. You do not need to install Tcl or
Tk separately on your system.

These design decisions have resulted in a software package that is
exceptionally portable and can be integrated into new environments with a
minimum of modification to the source code.